Split implementations from generic code

core/pkg/ingress/status/election.go

@@ -0,0 +1,119 @@
+/*
+Copyright 2015 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package status
+
+import (
+	"encoding/json"
+	"os"
+	"time"
+
+	"github.com/golang/glog"
+
+	"k8s.io/kubernetes/pkg/api"
+	"k8s.io/kubernetes/pkg/api/errors"
+	client "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
+	"k8s.io/kubernetes/pkg/client/leaderelection"
+	"k8s.io/kubernetes/pkg/client/leaderelection/resourcelock"
+	"k8s.io/kubernetes/pkg/client/record"
+)
+
+func getCurrentLeader(electionID, namespace string, c client.Interface) (string, *api.Endpoints, error) {
+	endpoints, err := c.Core().Endpoints(namespace).Get(electionID)
+	if err != nil {
+		return "", nil, err
+	}
+	val, found := endpoints.Annotations[resourcelock.LeaderElectionRecordAnnotationKey]
+	if !found {
+		return "", endpoints, nil
+	}
+	electionRecord := resourcelock.LeaderElectionRecord{}
+	if err = json.Unmarshal([]byte(val), &electionRecord); err != nil {
+		return "", nil, err
+	}
+	return electionRecord.HolderIdentity, endpoints, err
+}
+
+// NewElection creates an election.  'namespace'/'election' should be an existing Kubernetes Service
+// 'id' is the id if this leader, should be unique.
+func NewElection(electionID,
+	id,
+	namespace string,
+	ttl time.Duration,
+	callback func(leader string),
+	c client.Interface) (*leaderelection.LeaderElector, error) {
+
+	_, err := c.Core().Endpoints(namespace).Get(electionID)
+	if err != nil {
+		if errors.IsNotFound(err) {
+			_, err = c.Core().Endpoints(namespace).Create(&api.Endpoints{
+				ObjectMeta: api.ObjectMeta{
+					Name: electionID,
+				},
+			})
+			if err != nil && !errors.IsConflict(err) {
+				return nil, err
+			}
+		} else {
+			return nil, err
+		}
+	}
+
+	callbacks := leaderelection.LeaderCallbacks{
+		OnStartedLeading: func(stop <-chan struct{}) {
+			callback(id)
+		},
+		OnStoppedLeading: func() {
+			leader, _, err := getCurrentLeader(electionID, namespace, c)
+			if err != nil {
+				glog.Errorf("failed to get leader: %v", err)
+				// empty string means leader is unknown
+				callback("")
+				return
+			}
+			callback(leader)
+		},
+	}
+
+	broadcaster := record.NewBroadcaster()
+	hostname, err := os.Hostname()
+	if err != nil {
+		return nil, err
+	}
+	recorder := broadcaster.NewRecorder(api.EventSource{
+		Component: "ingress-leader-elector",
+		Host:      hostname,
+	})
+
+	lock := resourcelock.EndpointsLock{
+		EndpointsMeta: api.ObjectMeta{Namespace: namespace, Name: electionID},
+		Client:        c,
+		LockConfig: resourcelock.ResourceLockConfig{
+			Identity:      id,
+			EventRecorder: recorder,
+		},
+	}
+
+	config := leaderelection.LeaderElectionConfig{
+		Lock:          &lock,
+		LeaseDuration: ttl,
+		RenewDeadline: ttl / 2,
+		RetryPeriod:   ttl / 4,
+		Callbacks:     callbacks,
+	}
+
+	return leaderelection.NewLeaderElector(config)
+}